1. Field of the Invention
The present invention relates to optical control systems used in optical apparatuses, such as television cameras, video cameras, television lenses, video lenses or the like, that can perform automatic focus control (referred to as “AF control” in the following) as well as manual focus control (referred to as “MF control” in the following).
2. Description of Related Art
Optical apparatuses are known which have an AF control function, such as the optical apparatus disclosed in FIG. 1 of Japanese Patent Application Laid Open No. H9 (1997)-65184, for example. Moreover, there are optical apparatuses which perform focus control of an image-taking optical system by extracting, from the taken video signals, a signal (high-frequency components) related to the sharpness of the object, which corresponds to the focusing state of the image-taking optical system, and evaluating that signal, in order to perform AF control.
An example of this AF control is explained with reference to FIG. 8. In FIG. 8, reference numeral 1600 denotes a video camera with integrated image-taking lens. Reference numeral 1102 denotes an evaluation value generation circuit, which generates a sharpness evaluation signal from a video signal output by a later-described process circuit 1202, and reference numeral 1103 denotes an AF driving control circuit, which generates such a motor control signal that the sharpness evaluation value generated by the evaluation value generation circuit 1102 becomes maximal.
Reference numeral 1105 denotes a motor, whose rotation speed is controlled by the AF driving control circuit 1103, and reference numeral 1106 denotes a focus lens, which receives the driving force of the motor 1105 and is moved in the direction of the optical axis.
Reference numeral 1201 denotes a CCD, which photoelectrically converts object images formed by the image-taking optical system (not shown in its entirety in FIG. 8) including the focus lens 1106. The process circuit 1202 processes the output signal from the CCD 1201 and turns it into a video signal in accordance with a predetermined format, such as NTSC or PAL format. Reference numeral 1203 denotes a recording/reproducing circuit, which records the video signal output from the process circuit 1202 onto a recording medium, such as a tape, a semiconductor memory or the like.
In the above-described structure, light flux which has passed through the image-taking optical system (focus lens 1106) forms an image on an image-pickup surface of the CCD 1201, and after being photoelectrically converted by the CCD 1201, the signal output from the CCD 1201 is sampled and held and input into the process circuit 1202. The process circuit 1202 processes the input signal into a video signal of the predetermined format, and outputs the video signal to the evaluation value generation circuit 1102 and the recording/reproducing circuit 1203.
By filtering the input video signal, the evaluation value generation circuit 1102 generates, at vertical synchronization units of the video signal, sharpness evaluation value signals related to the high-frequency components of the video signal, and outputs the sharpness evaluation value signals to the AF driving control circuit 1103. While driving the motor 1105 to move the focus lens 1106 by incremental steps, the AF driving control circuit 1103 compares, at vertical synchronization units, the sharpness evaluation value signals, which are successively input from the evaluation value generation circuit 1102, and moves the focus lens 1106 to a position where the sharpness evaluation value becomes maximal. Thus, the focus lens 1106 attains an in-focus position.
The recording/reproducing circuit 1203 records the video signal output from the process circuit 1202 to a recording medium. It should be noted that the recording/reproducing circuit 1203 also performs the reproducing of video recorded on the recording medium.
A camera system performing such AF control is disclosed in Patent Document 1, for example.
There are furthermore optical apparatuses for special applications, such as surveillance, which can be operated remotely. Many of such optical apparatuses are not equipped with an AF control function, and in this case, they are configured for remote control of the focus, with the user operating a switch or knob or the like provided on a remote control unit.
A system adapted for such remote focus operation is explained with reference to FIG. 9. In FIG. 9, structural elements that are the same as in FIG. 8 are given the same reference numerals as in FIG. 8 and are not further explained.
Reference numeral 1400 denotes a remote control unit, which supplies command signals for driving a zoom lens, an iris (not shown in the drawings) and the focus lens 1106 of the image-taking optical system to a camera 1600, from a location that is at a certain distance to the camera 1600.
In the remote control unit 1400, reference numeral 1401 denotes an MF command signal generation circuit, which generates an MF command signal in accordance with the operation of a switch or a knob (not shown in the drawings), and reference numeral 1404 denotes a remote control-side connector, which is connected to a remote control cable 1500, and through which the MF command signal is output to the camera 1600.
In the camera 1600, reference numeral 1107 denotes a camera-side connector to which the remote cable 1500 is connected, and reference numeral 1109 denotes an MF driving control circuit, which generates a motor control signal for driving the motor 1105, based on the manual focus (MF) command signal from the remote control unit 1400. The focus lens is moved in the optical axis direction by driving the motor 1105 with the motor control signal from the MF driving control circuit 1109. Thus, it is possible to perform MF control by operating a switch or the like on the remote control unit 1400.
In the above-described remotely operated system, an electrical interface is established between the remote control unit and the camera, and the number of connecter pins (terminals) is set to twelve. And in their current form, the command signals for zoom, iris and focus, as well as the various control mode signals (for switching high-speed control and position control, for example), power and ground are assigned to these twelve pins, and there are no free pins left.
Therefore, when trying to equip the above-described remote system with the AF control function illustrated in FIG. 9, then it is not possible to assign a pin to a signal for switching the driving of the focus lens between AF control and MF control from the remote control unit, which is a new signal that needs to be sent from the remote control unit to the camera. That is to say, it is not possible to make a selection between AF control and MF control from the remote control unit.